H2–HCl 凡德瓦錯合物之全初始化互相作用能曲面

Abstract

一個六維H2–HCl錯合物之分子間互相作用能曲面已被提出。全初始化計算點完成於六維的網格，包含了H–Cl及H–H 距離的相關。首先，利用高效率明確相關耦合簇超分子方法(efficient explicitly correlated coupled-cluster supermolecular method (CCSD(T)-F12b)) 及大基底函數組，通過外插法計算出互相作用能。接著，三重迭代及四重非迭代激發貢獻，由較小的基底函數組計算得出並且加入。此研究中也包含了內層電子互相作用及相對論修正。所得到的互相作用能接著對HCl及H2之基態振動波函數進行平均。 由此進行解析擬合，產生四維勢能面。在勢能井，對應到真實完整基底函數組的不確定性小於0.6波數。藉由我們提出的兩步擬合，勢能面的形貌及能量皆能正確地呈現。擬合步驟在勢能井最大誤差及平均誤差分別為0.47cm-1及0.0066 cm-1。擬合使用簡單的三角函數。這些簡單的三角函數在未來工作中容易進行操作。相似的互相作用能曲面可以依照本論文中所發展的方法來產生。

A six-dimensional intermolecular potential energy surfaces for the H2–HCl complex is presented. The ab initio points have been computed on a six-dimensional grid including the dependence on the H–Cl and H–H separations. The interaction energies were first calculated using the efficient explicitly correlated coupled-cluster supermolecular method (CCSD(T)-F12b) with large basis sets, followed by an extrapolation procedure. Next, a contribution from iterative triple and noniterative quadruple excitations was added from calculations in smaller basis sets. The core electron correlation and relativistic correction were also included. The resulting interaction energies were then averaged over the vibrational ground-state wave functions of HCl and H2. The final four-dimensional potential energy surfaces were fitted by analytic expressions. In the potential well, the uncertainty corresponding to the true complete basis set limit is less than 0.6 cm-1. We proposed a two-step fitting procedure which reproduced well both the correct shape of the whole potential energy surface and interaction energy itself. The maximum error of the fitting in the attractive part of potential is 0.47 cm-1 and the mean error is 0.0066 cm-1. The simple trigonometric functions were used which are easy to manipulate in future work. Similar interaction energy surface can be produced based on methodology developed in presented Thesis.